322 PHYSIOLOGY OF BACTERIA 



In Sattler's experiments, the temperature of 80°C. is so high 

 above the maximum temperature that the temperature coefficient 

 of the death rate must have fallen to nearly normal. 



It is possible to compute temperature coefficients also 

 from endpoint experiments provided that they all have 

 the same initial number of bacteria. Under these 

 circumstances, the initial number, as well as the final 

 number, is the same, the only variable at different 

 temperatures being the time required to reduce the 

 cells to the same number. The formula for the death- 

 rate can be applied to the two temperatures which, for 

 simplicity's sake, shall be assumed to be 10°C. apart, 

 and we obtain 



where t^ and t'^ are the two disinfection times at the two 

 temperatures. The temperature coefficient is the quo- 

 tient of the two, and since log a and log b are the same in 

 both equations, 



Qio = Y 



For temperature differences other than 10°C., the for- 

 mula of p. 120 must be applied. 



Since the temperature coefficient is an exponential function of the 

 temperature, a straight line should be obtained if the logarithms 

 of death-rates were plotted against temperature. The above 

 formulae show that the death rates are proportional to the times 

 required for killing, and, therefore, the logarithms of these times 



